Automatic telephone system



April 18, 1933 v. s. THARP Er AL AUTOMATIC TELEPHONE SYSTEM '7Sheets-Sheet l Original Filed Jan. '7, 1929 HOlOFN/VOD 0l MSMQQN U`April1s, 1933. v. s. THAR'D am. 1,904,904

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. '7, 1929 7 Sheets-Sheet 2POLAR/IED X OFF/cf Claret-Lr: e E. Lomax.

April 18, 1933- v. s. THARP ET AL AUTOMATIC TELEPHONE SYSTEM 7Sheets-Sheet 25 Griginal Filed Jar). 7, 1929 UTB-1F11 E. Thap Elan-'aune.EL MAJ-415m; y

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April 18, 1933 v. s. THARP ET AL.

AUTOMATIC TELEPHONE SYSTEM '7 Sheets-Sheet 4 N 0%.. 1mi lll www Em wwwwww u www N MQ mswkm .m

April 18, 1933. v s THARP ET AL 1,904,904

AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. '7, 1929 7 Sheets-Sheet 5z oFF/cf UWE? E. Thal-I Clarence E. Lnmax April 18, 1933 v. s. THARP ErAL AUTOMATIC TELEPHONE SYSTEM Original Filed Jan. '7, 1929 7Sheets-Sheet 6 dmwllwlm. Milli.

nUEr-Llnrs' Uu: nr 5. Thap Clarence E'. .Lomax lApril 1s. -1933f v. sTHARP n M 1,904,904V

AUTOMATIC TELEPHONE SYSTEM original Filed Jan. '7, 1929 7 Sheets-Sheet 7YaFF/cf C2 l -...E04 j Patented prl8, 1.933

UNITE-n f c l l vieron s. Timm, or' n'LMHUnsT, AND'CLRENGE E.LoMAxoF/oax- Plink, L'LLInos.

I Assreivons BY MEsNE Asseivmajnrs; To Assocmrrnn nnncrrnliofnaomroninsY i 1Nc.,.or sarcasm-immers,AcoaPoRATzoNoF DELAWARE AiIroMATicfTELEPHONE SYSTEM f Applica-tion mea January a, ,1929, serial No;330,343'. 'nenewkiseetemteflii; 1931;.: p

-The present invention relates in general to y mnlti-ofice telephoneVsystems, .but isconcernedlmore particularly with telephone systems inwhich callsare extended through the medium Vot automaticswitches. ThemainV features of theinvention `relate to multi-.ollice systems in whicha calling subscriber may be charged for completed calls according to the,e actual durationof the call and also according 13 to` thelocationofthe office or exchange inr which the -called line terminates.V

Ininultioflice telephone systems it is. sometimes desirable to make` afixed charge for,

`completed `calls withinan exchange orbetween several exchanges'relativelynnear to# gether `in the same area or zone, ,whilec'alls fromexchanges in one zone to exchanges 1n-l 'a diil'erent zone-may be`charged `for on the Y, basis loi" the durati'onof` the call.

20 A suburban servicemay be provided whereby calls will beextendeddirectly by amanual operator to a subscriber'in a semi-distantexchange without setting up the usual toll con-v It is customary to makea greaterl charge for calls of this type than is made forA calls betweensubscribers .in the same townorA system of exchanges. The additionalchargeV nections.

may be made by keepnga written record of each call `or by providing. ameans 4by `which 3U tlie'operator may Acause the subscribersmeter toVregister additional call units. l The latter f method is preferable asit eliminates the necessityofverifying the number of the'calling' Vline.'i

he present invention is particularly effec-v tive in a systemofthe-above type, as itprovides for automatically` registering theproper. Echarge for local and inter-zone calls,'

and also provides asimple means whereby an` 40- operatormay malreanadditional charge on.

suburban calls.

` One object of the invention is toimprove systems oflthis general`characterpby pro,

l viling simplified circuitslby which the meter-Q 45 ing operation maybe accomplished.

Another object' of the inventionfis to` provide circuits whereby callsmay be extended automatically'from one exchange to another r through anintermediate exchange, the meter! '50i ing. operationbeing effected byapparatus in the intermedi,ateexch-angeV which in'turnf'i's a controlledfrom the termiatingexchajgnge. I

Another objectof'the inyention ist'ojprovide a'means whereby an operatorati a manualor toll 'board' may position the `ref)eater through which acall is extended-from an out@ lying exchange VV'so that meterregistrations will automatically be inereasedwhen thecall isfurtheriextended to semi-distant" xg, change."A 'l' n Y practical..

The foregoing features together others not specificallymentioned willbemere-1 fully pointed outhereinafter. v Y

The accompanying drawings comprising Figs. l to 9,"in`clusiv'e, shew-.bymeansoflthe usual circuit diagrams,` a' Asullicient' amount of,

equipment in fa telephone system Vvembo'dyi/'ng` the features oftheinvention to enable` the-f inventionto; be understood;

, Forthe purposeof thisdescriptionitis assumed that'theequipment'embodying tliefV invention is locatedl in three separate .1 exi"changes which `will be designated as .oflices X,2Yand Z, respectively.Itis to be "under' stood, however, that the rapplication ofthe inventionis not limitedto thisparticularvar rangement but that it maybbeused withother y combina-tions' of `equipment and in systems V` comprising adifferent nui'ber of exchangesjj from that described herein. L L

y rig. ianathat portion einig; 'saying the leftofthe heavy broken'lineequipment llocatedfin X oilice.V Fig.` 2 tothe right ofthe-'heavy brokenline fand vFigsJBQ l 4:,6 and 7` show equipment located inf Yfof-f ffice.v The equipment in Z oiiicefis- Shown in' Fig. 5.- F 1g. 8 showsthe method of straps- Y ping the test contacts of the banks of switch? iing connector C off Fig. 1.` Fig; 9""is a layo'ii't',4

diagram showing-.how the sheets on which? i .Y Figs. l to 7,` inclusive,are'drawnfshould'be placedtogether in lorder tobe undeifstonfidi best;

Referring particularly to` Fig-LA and AQ? a represent ordinary automatic'substatio'iisf equipped with usual talking, "signalling K and impulsinginstrumentalities rand individually connected to line switches LS andLS1, respectively. The line switches are of the well known rotary typeprovided with a meter .controlled over a separate wiper of the switch.

Mechanically, connector C is of the well known Strowger vertical androtary type. The circuit is similar to the ordinary switching rotaryconnector with modiications to provide a quick switch-through on trunkcalls. This feature is superior to the switching-through methods used inprevious connectors since the quick connection to the succeeding switchminimizes'the chances of mutilating or losing a dialed vdigit whichmight occur in case of delay in extending the trunk.

. In Fig. 2 is shown an outgoing repeater OR and an incoming connectorC1 associated with the end of a` trunk terminating in X oiiice. rThe'incoming repeater IR and Voutoutgoingirepeater OR1 are associated withthe other end of the trunk inYotlice. The circuit of repeater ORl issimilar to the ordinary loop repeater modified by the addition of arelay whose function is to provide a special means of metering.`Connector C1 is identi- Ycal with connector C. Only that part of theerating loop circuit is switched to a simplex i for metering purposes.VThis selector is in holding circuit. Metering impulses are repeatedvback tothe calling line by removing the potential from the simplexholding cir- 1 cuit.

Repeater OR1 is' connected with the trunk only when a call isextendedtherethrough,

and inY this case, re eater TRis disconnected from the trunk. epeaterOR1 extends a g; loop circuit overV the trunk to operatecon- 4 nector C1Y1n the usual manner.

peaterV 1s also arranged for metering over f This retheV fourthvconductor of the incoming trunk. Referring to Fig. 3, incoming selectorS iis `an ordinary Strowger type selector provided witha separateconductor and Wiper the same office and is directly associated withincoming repeater IR. The loop extended 5 bythe repeater controls theoperation of the selector-'in the usual manner, and when an idle trunkis found, the loop is extended to the succeedingswitch free Aofanyconnec- ,l tions-in the selector.

Fig. 4 shows an outgoing repeater, OR2,

and an incoming repeater TR1 associated with a two way trunk. Theseswitches are assumed to be in Y oiiice, the associated trunk extendingto Z olice. Repeater OR2 is accessible to both local and incomingselectors in Y otice. Associated with and a part of repeater CB2, is atime pulse metering device M consisting of al rotary switch RS andasso--` ciated relays. On calls extended through the repeater, theoperation of the time-pulse device under control of the interrupter INTcauses metering `impulses to be transmitted back to the calling line atcentain preestablished intervals. On calls to an operator the rate atwhich metering pulses'are sent out can be increased to twice` the normalrate under the control of the operator.. As

shown, the repeater is normally disconnected from the trunk, but when acall is extended thereto, the cut-olf relay of theV re-v peatertransfersthe trunk from incoming repeater TR1 to repeater OR2. l

Repeater TR1 is a simple repeater operating over a loop to which batteryandl ground are connected atv thefdistant office'.

The repeater extends a loop to'incoming selector S1, and controls it inthe usual man ner. The circuit of selector S1 is exactly the same asthat of selector S shown in Fig. 3.

Fig. 5 shows equipment located in an exchange of the type in'whichdialed impulses: are repeated by the first selector to succeeding`switches of the train.

Incoming repeater TR2, normally associated with the trunk operates overthe loop extended by repeater CR'2 and' extends a control circuit toselector S2. Dialed impulses are repeated as ground impulses over aconductor of the trunk while a holding circuit ismaintained over theothertrunk conducf tor. When a call extended through the repeater isanswered, a ground potential placed Y on one trunk conductor by theconnector op- Y This relayv erates a relay in the repeater. shortcircuits a part of the winding ofthe relay controlled by theloop fromthe preceding switch and thereby increases the current flow in thetrunk. They increase in current flow is used to operate the meteringequipment in the preceding switch.

Selector S2 is mechanically similar to the previouslydescribed'selectors S and'S1. The circuit, however, is of the wellknown' type used in the systemof Siemens & I-Ialske.

Selector S2 hasaccess to theusual switch train in .an oiiice of thistype comprising selectors S5 and connectors C3 which, being well known,will not be described in detail.

Succeeding selectors may be identical .with

selector S2. A connector which will operate.

satisfactorily in this system is shown on page 46 of the illustrationsection of Dr. Fritz Lubbergers book Die Fernsprechanlagen lio Bfr

Mit Whler-Betrieb (Automatische Tele-` phonie, third edition, 1926. Y

A"Selector S2 also has access to trunkste'rminating in anoperatorsposition',a part of i theoperatorls answeringequipnient,.OA,'be-

ing shown. It is assumed that all tolfl and suburban calls for thesystem will be handled atthis-oper-ators position which is located inZoiiice. n y An operators calling circuit, 0C, Valso has` access tothetrunk to4 which repeater IRE' is connected. V'When the trunk is used`by'the operator the repeaterisA disconnected,y and when the repeater isin use the operators cir; cuit is disconnected and the operatoris'informed-by 'a usual Visual signal offthe busy conditi'on'of the trunk.Calls from substationsfsucli-as A4 in Z olice to substations in X-and Yoflicesfwill be completed bythe operator.y The operator extends callsover` the, trunk by means of al loop toy whichVV batter'y fand groundare connected at the man ual position. i

In Fig." 6, selector l by a rectangle, isY identical with selector S. Agrepresents substation vin Y otiice ter- Ininatijng'in rotary lineL'switch VLSg Which inA tury'has access toselector SQ.' Substation A2`and line switch LS'Z are exactly the same as previously describedsubstation A and line sWitchLS.' l y v"In 7, C2` represents alocalconnector of the ordinary Strowger type arranged for` fourth wiremetering. The connector is assunied to be in "Y cnice-land has access tosubscribers' lines of whichsubstation A5 terl-f4 minating in rotary lineswitch LSI is one,` The connector is accessible "inthe banks of localselector S4 and incoming selectorsS and S1 Aall'in vY oHice. iSubstation 4AaQand -line switch DS3 arethe same aspreviously describedsubstation A and line switch LS.Y

The Various units: ofpequiplnent and their locations -with relation to.each other Vhave "been briefly described. The arrangement and,

operation ofthe, system as a whole will now befconsidered. n l i Olice`X is assumed ,to be a branch exchange connected bymeansoftwoconductorftrunks with loilice Y,`a main exchange. Office Y isprovided with: trunks to other main` exchanges such asuZ cnice.`Inter-oiiice callsf originating in X,oiiice Will be routedv`Ythroughequipment in Y oiiice in aA manner comin-only known-as tandemtrunking-.

l'The equipment Vin X and Y oiiices is of the twowire type in which ktheVarious `switches. are directly controlled by the calling zsubsoribcrover the two sides ofthe line in serieslV Eqtiipnientfinthe Z office-isof the type in whficliftheist' selector only is directly con-` trolledbyythev calling"1 subscriberl oyer the two sides of' the line inSeriesTSuCceeding' switch-es 'are controlled by impulses repeat-M edbythe vfirst"selectorfand transmitted severi'.

one sidelofithe tr.unk.xfV i Calls may be completedfautomaticallyin:

'and between Xand oliicesrand ffrom'either v of these oliices toZoliice:.-Localfcallswin office may be. completedautomaticallybruti`calls from .this office to .feitherf X are completed manuallyLwone meterregistration is made for each# coinpletedl callregardless of duration.lOna-calls: c

from 'eitherfof theseoiiices to asubscribei's y i `inZ oiiiee, oneineterregistration is made as? Vsoon as the call is answeredwithl an;addition!-v 'i al registration for each time. unit over-"thc basicv timeinterval. The time intervalmayf be set within any reasonable'limit. fLocali. f calls' in the Z `ollic-zfinay be' metered lby any" of themethods ordinarily-used in exchanges: of this type.. Y' f' Suburbancalls, p ers in `other nearby cities `of thisfsystemor p A Qthersystemsare completed by afmanualor Si which is representedr toll operator-inZoiiceJCa'll's of this class; originating kin X jor YV` offices'arerextended over rthe regular inter-ofiice trunks I andA through-theswitch train at vZ ofiicetothe-ly manual or toll position. Thev operatormay position the repeater at Y oiiiceithrou'gh which? the call wasextendedso'that the metering` charge ordinarily registeredfforcalls toZ55 oilice will be doubled. f

Having explained the object vention and the apparatus employedfthe:operationsinyolved'in setting; up .various connections in a system ofjthis type will new? bcdescribe'd inldetail.l 1

'Assumin' -first that the subscriber'atsub-Z station A Fig.1).in Xoiice'calls'thesub'f; scriber A4 inA Z 'office (pF `ig.5).1{VV'hentheV ductorsof the vcallinglline and line-switch;

that is; @aus te jlitsefitfV esi or alle in;

LS 'searches for an idle trunkinthelusual manner. When an' idle trunkisencounteredf,

for example, the trunkco'mprising conducf" l tors 18to21,'inclusive,'the calling loopfis exif tended to line relay 103 ofconnector Y Line relay 103, release relay 104.v and# change-overurelay105 of the connector' are energized `in the usual manner. Relay 104iconnects ground to the release trunk at arma-- ture=130A to hold thecut-oil'lrelay-ofthe linev` switch in operatedposition;V Relay10A-alsof? closes a part vof the impulsing circuit at armature 132,relay 10.5 disconnects ground from 12a ture 181. V-At contactscontrolledby arma Y* f the low-er Vwinding of relay 103'anfd5 connects'thereto vanother ground Von. which ,the-diet` l' tone is superimposed??AtarmatureV 134 fre= l lay 4105V connects the-impulsing circuit'to? ve`rtical `rnagn'etrllQ and at arm-ature'133 con-'f d .nects its own lowerwinding toathe'impuls ingfcircuit in'parallel Awith?thevertical mag'-net.` YThe" foregoing operation takes place"v 1'65A receiveris lifted atthesubstation A, theV 1 usual loop circuitis cl-osedover the twocon'fhvwhen the receiver at the calling substation is lifted and the connectoris then ready to receive the dialled-impulses. It. will be assumed thatthe calling subscriber now dials the digit The calling loop will beopened ten times and line relay 103 of the connector will respond bydeenergizing and reenergizing with each interruption of the loop. Witheach deenergization 19, 0f relay 103,.the. vertical magnet will operatein the usual manner and raise the shaft one step at a .time until Vthewipers are opposite the tenth level of bank contacts. The initialenergizing winding of relay 105 is short cir- :ti cuited at .contacts119 of the off-normal `V springs which closed on the first verticalstep. Relay 105! does not -deenergize at this time since vits lowerwinding isconnected in parallelwith the vertical magnet and due to its2,9; slow releasing character, the ground impulses tothe vertical'magnetare sufiicient to keep it energized during the period of impulsing.Shortly after the last impulse of the series,

relay 105 deenergizes and disconnects its 2.5; lowerv winding from theimpulsing circuit at armature 133, and at armature 134 switches theimpulsingcircuit to rotary magnet 113. Upon restoring, relay 105disconnects the dial tone ground and reconnects the ordinary .39.:ground to the lower winding of relay 103.

Relay 104 being slow to release also remains energized during the seriesof impulses when its circuitis opened by the impulsing of relay 103.v K

As the wipers are stepped to the tenth level, the shaft springs .operateand contacts 122 close a part of the circuit of relay 101, which,

A Relay 107 deenergizes, opens its ownlocking.

however, does lnot operateat this time. part of the metering circuit isalso lopenedby I the shaft springs-at contacts 121.

l It will now be assumed that the tenth level ofthe connector banks isequipped with four trunks terminating inthe repeaters such as OR, andthat these trunks are connected to 45.-

, level. vThe subscriber now dials theA digit 1. Relay 103 Vresponds inthe usual manner and the rotary magnet is energized-v o'ver a circuitincluding armature 131 i of relay 104, armature 134 of relay105,armature 143 lof relay 108, winding of relay109, and Varmature 157 ofrelay 111. Slow release relay 109 energizes in series with the rotarymagnet and at armature 145 opens a point 1n i the circuit of the lowerwinding of relay'110.

At armature 146 a Vcircuit is closed for theV upper winding ofrelay 110,and at armature 147. a pointin the circuit of relay 107 1s opened. Theutility of the last operation will be described in more detail later on.,l Y

. Relay V 'operates' and atV armature 148 closes a point in the circuitof its own lower winding;.at armature 149 connects test wiper 117 totest relay 108; ,atarmature' 150 closes 5.513 a point in the lockingcircuitof its own ulp-v the first four sets of bank contacts of they perwinding; at armature 151 closesy avcircu'it for the rotary magnetindependent of ther contacts of the relay 108; at armature 152 closes apoint in the circuit of relay 107 and:

at armature 153 opens apoint in the busy tone` circuit. Y

' If the trunk on which the wipers stop is busy, test wiper 117 willfind a ground'fpo-v tential. Test relay 108 will operate from this,

one, slow release relay 109 deenergizes. lIfhev lower winding of relay1170 is then connectedl to control wiper 118 by way of armature 145 ofrelay 109. Relay 110, however, has no function to perform at this time.At armature 146 relay 109 opens the initial energizing circuit of relay110 and at armature 147 closes a circuit for relay 107 includingarmature 152 of relay 1 10 and the' interrupteif springsof the rotarymagnet. Relay 107 ,op`

erates and armature 139 closes a circuit for the rotary magnet includingarmature 157 of relay 111, and at armature 140 closes a'- lockingcircuitfor itself including the interrupter springs of the rotarymagnet. .The

rotary magnet energizes, steps the wipers'to the next setof bankcontacts, and' opens the circuit of relay 107 at its interruptersprings.

circuit, and opens the circuit ofthe rotary magnet which alsodeenergirzes. If the Vnext trunk is busy, the above described operationlis repeated, relay 107 and the rotary magnet alternately energizinganddeenergizing to step the wipers ahead a step at a time.

If all trunks of the group are busy, the wipers are stepped to the setof contacts following the last trunk of the group. Inthis'` case thebank contacts with which wipers 117'V and 118 are engaged arestrappedtogether and connected to ground 4as shown in Fig. 8.

Relay 108 willr remain energized from this' ground over the test circuitpreviously traced. A' current will also flow in the lower windingl ofrelay 110 over a previously ltraced 'control a previously 'tracedlocking circuit for reg lay 108 including contacts controlled byarmature 149 ofrelay 110 and armature 141-ofy relay 108,v opens thecircuit for relay 4107 at armature 152 to prevent that relay from againenergizing-and operating the rotary magnet, and at armature 15.3 closesapart of the busy tone circuit. The busy tone is now givento thecallingsubscriber who is thereby informed that lall'ftrunks are busy atthis time'. 'l y 'If a trunk hadV been idle, for example, the trunkcomprising conductors `167 to 1.70, inclusive, terminating inV bankcontacts 159 t0 162, inclusive, the wipers would stop on these contacts,the'operation being as follows: f

VAn idle liner is marked'bybattery poten- .tial Vonthe testcontacts. Ifthe lirst trunk is idle, wiper 117 encounters the -batterypotential onthe test contact andfrelay 108 does tnot operate. Shortlyafter theflastrotary impulse, relay 109 restores. 'I`l","l1oweVer, Vbusy trunks hadbeen tested previousto find- Iingtlie'id'le trunk, relay 108 would beenergized and relay 109 deenergized as previ-` ously described. Relay108 thendeenergizes `when wiper 117 encountersrthe batterypoten- 'tial.on the test wipers; ith'both relays 108 and 109 restored to normal,thecircuit of relay 110 will be openand relay 110 deener- Ygizes.VA'circuit may then be traced from battery on uthe test contact,wiper117 armature* 149 of relay 110, lower winding of relay 111, toground at armature-130 of re- -circuit and `at armatures 154 and 158connects #the talking conductors of Vthe uconnector to .wipers 115 andl116;at armature 155 connects test'wiper 117 to the release trunk; atarmature `156 .connectsits own upper winding to the release trunk andclosesa circuit Vfor IIrelay 101, including contacts l122 of theoperated shaft spring, and opens the circuit of the rotary magnet atlarmature 157. The upper winding of relay 111 now maintainsit inoperated position. Relay 101* operates and, at ycontacts controlled byarmatures123 'andf126, switches the conductors of the callloop fromrelay 103 .to Wipers 115 and .116;fat armature 124 connects meterconductor-21 to wiper 118; and at armature 125 opens apoint in thecircuit of the release mag- 'net. After relay 101 operates,`relays 103and f 104 :(leenelgize. Relay 104 being 'slow to i 'i .restore, willmaintain theholding ground' on the release trunk until-a groundis'returned by the switch ahead. f These relays upon *restoring alsoclose points in the release circuit at .armatures 129 and 131. Thecalling line loop is now extended directly'to line relays 202 of therepeater OR by way of Wipers 115 and 116, contacts 159 and 160,vconductors 167 and 168, lefthand Windingsof repeating coil R, andcontacts controlled by armatures 212 and 213 of relay 20,1. Meteringconductor21 is extended' by way 'of Wiper 118, contact .162, `andconductor 170 to a contact at armature 215 of relay 201.V

Release trunk conductor 20 is extended by j way of wiper117, contact161, conductor 169,

lay104. Relay 111 operatesover the, above `operates over the `loopcircuii-gextenddmby `right hand winding of repeating,coiljRgxare',connects the ground to `the *releasef' to contacts at armature 219ofrelay 204, andl thence through normally closed contacts 130 `of relay104 in incommgconnector C1, 'to

relay 205@ `Relay 104* corresponds Withrelay 104 vof connectorV 'Relay104 of con-frm 'nector C, as previouslyy explained, hasmainv j tained aground on releasetrunkfor a short interval after the vconnection is Yextended.

Relay 205 operates from this groundand switchesrtrunk conductors 207 and'208 from i75 the incoming connector C1 to talking conductors of therepeater'OR.' Y Y' Y Relay 202energi`zes over the calling loop and atarmature v216 l closes a point vr'1n the vj loop circuit totherepeaterIR inthe vdistant oiiice,"and1at armature 217 closes an obyiousvcircuit Vfor relay 204. Relay 204 operates `and atarmature v219vconnectsy ground to the Vrelease trunktohold the lpreceding switches rfvin operated position Aand to keep relayf-205 j energized afterrelay104'ofconne1ctorGldeenergizea At armature 220 relay 204: lso

closes a `circuit for the upperl win'dirigslof relay 203including!armature,` 211101? "relay the high resistance in the circuit.y

Line relay *236 of incoming 'l repeater *,"IR

the repeaterOR. This circuit jmay'betaced as follows battery,:upperwindingof :relay 236, contacts controlled'by armature 245 of e relay234,1upper left hand winding `of-*ref Y peating coil R1, armature268of'cut-oli relay M y 261 in repeater OR1,gthence voverthe'ftrunk 105.

conductor 207, `armature 223y of relay 205 in per right hand Winding ofrepeating coilR, upper winding o'fpolarizedrelay`201, lower ub mature221 of relay 204, armatureV 2240i? 're'- lay 205,'thence overtrunkconduc'torl-208y- ,Y armature 269 of relay 261, leftha'ndwinding ofrepeating coil R1, contacts controlledby armature 246 of relay 234,lower "Winding of relay 236 to ground. Relay'236 on operating closes aloop circuit to the succeeding Switch at armature 248 and atarmaturef249 ycloses,

an obvious circuit for relay .231." VRelay 231 operates andv at armature5238*' connects,"120 ground to y release trunkfconductor 252,v 2a branchof which extends'through'the lower winding of 4polarized relay 235.`VRelay' 235 does not operate atV this time, howeyer,fover itslowerwindin'g alone( At`armature239 125 -relay'231 disconnects relay 261of repeater OR1 from release trunk conductor282'-of 'the trunkincomingto thft repeater,war1d conductor to mark the repeaterbusy.

trunk in the usual manner.

The loop Vcircuit extended by the repeater armature 361 of relay 305 inselector S, low- .ergwinding of relay 301 to ground. Relay 301 operatesover the above-traced circuit and at .armature 351 closes anobviouscircuit ltor relay302. Relay 302 operates and closes the usual impulsingcircuit.

Thus the subscriber at substation A upon dialling the two digits 0 and 1is connectjed with incoming selector S in Y oiiice .through repeaters ORYand IR. The subscribers'loop controls relay 202 of the re.-

vpeater OR. Relay 202 controls the loop over whichrelay 236 of repeaterIR operates.

x-Thetwo loops are inductively connected by repeating coil R. Relay 236controls the loop over which. relay 301 of selector S operates. Thisloop is inductively connected vwith the loop between repeaters OR and IRby repeatingcoil R1. y Y

. It will now be assumed that the third digit dialled by thecallingsubscriber is the digit 0, vRelay 202 of repeater OR responds `toeach interruptionof the calling loop, devenergizing and reenergizing tentimes. With each deenergization of relay 202, the loop circuit to relay236 of repeater IR is opened and relay v236 deenergizes and reenergizes'in response.l VEach deenergization ofrelay 236 cpens the loop circuit ofrelay 301 o selector relay y301 deenergizing and reenergizing inresponse tothe interruptions. VThe impulses from the calling device arethus repeated to the incoming selector inthe distant oliice.

lSelector Sis of the ordinary Strowger type whose operation is wellknown in the vart. It is therefore thought unnecessary to describe itsoperation in detail. -Relay 301 Vresponds to the dialled impulses andthe ver tical magnet operates tof'step the wipers to the tenth level.Relay 304 and the rotary 4magnet'then cooperate to step the wipersontothe bank contacts and hunt for an Aidle When an idle trunk is found, forexample the trunk comprising conductors 329 to 332,' inclusive, relay`305 operates, disconnecting line relay 301 from the control loop andswitching the loop .through the succeeding switch.

The loop from therepeater IR is thereby extended to the line relay 404of repeater AOR2, circuitsof which may be traced as follows: battery,upper windingof relay 404, contacts controlled by armature 416 of relay405, upper left hand winding of repeating coil R3, trunk conducto-r 329,bank Contact 321, wiper 311 of selector S, armature 358 of relay 305,trunk conductor 250, thence through the loop in repeater IR over whichrelay 301 previously operated, trunk conductor 251, armature 361 ofrelay 305, wiper 312,i`

bank contact 322, trunk conductor 330, lower left hand winding ofrepeating coil R3, conp tacts controlled by armature 417 of relay 405,

through the lower winding of relay 404 to ground. Release trunkconductor 252 upon C which ground is rplaced by relay 231 of repeater IRis extendedby'way of armature 360 of relay305,wiper 313, bank contact323, trunk conductor 331, normally closed contact winding of relay 407to battery. Metering conductor 253 is extended by way vof armature 359,wiper-.314, bank contact 324, .trunk conductor 332 to contacts atarmature 418 of relay 405.

traced loop circuit and at armature 412 connects the upper windingo-frelay 402 to trunk conductor 428 by way of the upper right hand windingrepeating coil R3 and armature 425 5 Y of relay 407. At armature 413 vanobvious circuit is closed for relay 406. Relay 406`opcrates and atarmature'421 closes a point in and armature 457 of relay 453 through the'T80 Y i OR2. Relay 404 operates over the previously the circuit ofrelay 405, at armature 422vcon- -nects an additional groundY to releasetrunk conductor 331, at armature 423 connects ground to trunk conductor429 byl way of lower right hand winding of repeating coil R3 andarmature 427 of relay 407, and at armature 424 closes a point in thecircuit of relay 401. .I

The loop circuit is thus extended to revpeaterfIR2 Vincluding lowerwinding vof relay 503, contacts ycontrolled by'armature 513 of relay502, left hand windings of repeating Vcoil R5, armatures 511 and 512 ofrelay 501,

trunk conductors 428l and 429, armatures 425 and 427 of relay 407, righthand windings Vof repeating coil R3, to ground at armature 423 of relay406, and to battery through the upper winding of relay 402. Relay 402operates over ythe above-traced circuit and opens a po-int in thecircuit ofY relay 405'. Line relay 503 of repeater IR2 energize inseries with relay 402 over the previously traced circuit and at armature514 removes ground from th-e impulsing conductor ofthe repeater, and atarmature 515 closes an oby vious circuit for relay 504.v Relay 504operates and at armature 516 closes a point in the circuit of relay 506;at armature 517 closes a point in the circuit of relayY 505; at armature518 closes a circuit from ground through relay 507, conductor 510,oftnorinal contact 539 of selector S2, windings of relays 531 and 533 tobattery. Relay 506 is not on the impulsing lconductor of the trunk.

i `Relay 505 does not operate as `thecircuit is opened at armature515.of -relay :503. Relay ,507, however, operates over the above-tracedcircuitand atarmatures'A 524 and 525 connects trunk conductors 508 and509 to the repeater. `.The visual signal 582 operates from ground on.signal lead 581 to inform the `operator 'that the trunk is beinglused.

" lRelays 531 and 533roffselector VS operate in '.serieswvithrelay507`in the circuit previouslyV traced.v Relay 531, uponoperating atarmature 540conneots impulsing-rela-y 532 jtov Vtrunk conductor 508, atarmature 541 con- -nects itstownlower Winding to trunkco'nf :ductor509,-and atV armature 542 opens a point inthe circuit of the releasemagnet andn closes a pointlin the `vertical impulsing circuit. Relay 533upon operating. atarmature 545 connects relay5'34- to test Wiper 554,lat armature546 connects its own lower Winding and upper'Winding inseries with resistance i536 to control conductor 510,* and at armature547 closes a. point in the rotary circuit.

Incoming selector S2 VisV now readyatore- 'ceivey the callingsubscribers fourth digit. Assuming Vthat-the `digit nine is now ldialed,the interruptions of the calling loop will be 'repeated byrepeatersV ORyand IR as. pre- 4:viously described lto relay-404 of repeater ORL.Relay'404deenergizes and reenergizes in? response tothe repeatedimpulses. vWith `each ideenergization of relay 404,1thepreviouslyvtraced loop circuit of relay is opened at the armature`412 offrelay 404.

With each deenergization of relay`404 a circuit is closed for relay 401at armature '413, this circuit also includes armature 424 of relay 406.ARelay 401operates on the first deenergization `of relay 404 andremainsenergized during" the series ofimpulses due to its slow releasecharacter. `Relay401v closes a holding.; circuit for the floweriwvindingof relay 402 at armature 408. Relay'402- therefore remains energizedwhen its initial enen vgizing circuit is interrupted atthe contactsofrelay 404; Shortly after the last impulse Vof the series, relay401'deene`rgizes and opens the holding circuit of relay 402energized-over the loop. Y Y

As relay 404 opens its upper contactsI in response to the dialledimpulses, the circuit of relay 503 ofrrepeated IR2 will be opened a likenumber of times land relay 503 will respond. With each 'deenergizationof relay 503, a circuit Will be closed from ground,-

armature 514 of relay 503, upper right Yhand Winding of repeating coilR5, armature `524 of relay 507,;trun'kconduotor 508 to selector Slj,armature 540 of relay 531, -Winding of relay v532 ,tol battery. Alcircuit for relay 505 is also vclosed from grounded armature 515 ofrelay 503 and -armature1517 of relay A504. Relay 505 operates on theirstimpulse .and l:remains operatedA throughout :the 'series of impulses,due toits slow` release construcr tion.jf-;Relay 504 is also yslovvtoreleaselfa'nd -remainsoperated lwhen. its circuit is momen-,N Renytemlabove .traced circuit Ain response. totth'e-fvre- Y '.peatedimpulses-and closes the 1circuit of the 'vertical magnet a: like numberoftinies.: .The -lveitical magnet `operates fand steps fthe switchyfshaftand `Wipers 'upto' the calledlevel.; ffllhe '30olnormalv-'springs 539` and 1557"- operate' on the rst `verti'c'alstepof thelshaft fopeningthe initial energizing circuit ofrelays531` and'533iA `Relay V533,remainsenergized overt'he previously tracedlockingfcircuitincluding.imi

its upper` andlower xvlin'dingsl and'V `resistance 536 in series.'-VRelay531 remainsope'rated during the series'of impulses, it'slowerWinding beinge'nergized 'rol'n-batteryy vvon trun'kconductor 509. l e Yy Shortly after the lastlim'pulse of theseries', relay 505 ofrepeater-TR2 'deenergizes and Vopens the holding circuitof relay 531`which 'also deenergizes". Relayf531 on'fdeenergizing closes the usualrotaryv stepping y,circuit-and selector S2 searches foran idletrunkfi-nthe l usualmanner.y j- [f On," reaching-an idle trunk `which willfbeYassumed `to' -be that comprising vconduct'ons i561 *to 563, inclusive,`terminating von A"contacts'558 to 560, inclusive, relay534 'Wfilloperate over a-circuit includingrelays-inthe succeeding A'switch`corresponding to relays 531"and533 of Vselector S2. Relay534po1roperating ati armatures 548 and 549 switches trunk condu'ctors508yan'di509through to conductors 561 land 562 by Way of wipersr552 e and 553 andcontaets558 and559. Y f- 'if f g The trunk comprising conductorsl I561to 563, inclusive, 'extends tov a'regularselector vS5 of thelocalswitch train of office JZ. "This trainniay include one or moreranks Jof Aselectors and a-rank of connectors. the resi l `Inainderofthe digits are dialled by theca'lling subscriber,i'relay 503 ofrepeater I'RZTIesponds andrepeatsfthe impulses to` the lsuc# ceedingswitches* in' thev same manner as Idej-` scribed for selector S2.SeleotorSZ-icannfot operate from these impulses r,since impulsing relay532," is disconnected from the trunk at armature 540 ofrelay 531 `andthe energizing circuit vof relavi'5'31 is'open at 'the operatedoff-normal spril'gs.` v g -g Thefreinaining digits operate 1 the finter-f; f mediate selectors andthe 'connector' in afinanf- 125 nerWellVV known Vin the fartto connect with the/Wanted line suchv as A4."lIf'fthfe'lineis busy, a busy tone will lbe returned? by theflconiVnector to informthe 'calling partyf that" the Wanted line is :notavailable Whereonfthe C SI5 calling subscriber will replace thereceiver. Ifj the wantedfline-is idle, the connector will signal thecalled' station in the usual manner andreturn a ring-back tone to thecalling subscriber.

When the called subscriber answers, the ringing current is cut-olf inthe usual manner and the connector Vplaces aground on the upper trunkconductor. This ground extending back through `thelocal -switchtrain'over conductor 561, contact 558, wiper 552, armature 548 of relays534 in selector S2, conductor 508, armature. 524 of relay 507 inrepeater IR2,farmature 516 of relay 504, armature 520 of relay 505,resistance`523 to relay 506. Relay 506 operates and at armature l526closes a circuit for relay 502 including armature 518 of relay 504.Relay 502 operates and at contacts controlled by armature 513,disconrnects the lower winding of relay 503 from the -controlloop andconnects the upper and low'- `er windings in series across the loop.

As previously described, relay. 402 energized over vthe control loop inseries with the lower winding of relay 503. When both windings of relay503 are connected in' the circuit, the current ow in relay 402 isreduced and relay 402 deenergizes. Relay 402 on deenergizing closes acircuit for relay 405 at armature 409 and the armature 421 of relay 406.Relay 405 operates and at contacts controlled by armatures 416 Land 417reverses battery .over the loop vfrom repeater IR'by means of the usualreversing circuit. Relay 405 at armature 414`closes a locking circuit'for itself; Aat armature415 vcloses a point' inthe circuit of relay403which has no connects metering conductor 332 which extends back throughselector S to metering conductor 253, to a Contact in the left hand ,Ybank of rotary switch RS through resistance 436; at armature 419 removesVground from the right hand bank contactsof rotary switch RS; and atarmature 420 connects a lead from the interrupter to the rotarymagnet ofrotary switch vRS. Interrupter 'INT is adjusted to send out. groundimpulses at predetermined intervals. Each impulse 'causes the rotarymagnet 434 to energize. When the rotary magnet deenergizes after eachimpulse, wipers 430 and 431 are advanced one step in a counterclock-wise direction. On the first rotarystep, battery is connected to ameter lead. 332k by way of wiper 430, Contact 432, resistance 436, andarmature 418 ofrelay405. The rotary switchcontinues to step as long asrelay 405 vis energized Vand at each ltwenty-fifth step, closes theabove-traced circuit for the meter lead. It is obvious that the intervalbetween metering impulses can be varied by' adjusting the speed of theinterrupter or by attachingthemetering conductor to other bank contacts.p,

As vpreviously;-mentioned, relay 405 refunction at -this time; atarmature 418 verses the directionof ycurrent flow in the I control loop.The loop ras previously described,includ'es the upper winding ofpotrolled by armatures 245. and 246 reverses the Y trunk conductors 207and 208 with relation to relay 236, at the same time connecting theupper winding of relay 232 in series with the upper winding of relay236., Relay 232 op- Verates and at armature 240 disconnects its? upperwinding from the previously men-l tioned series circuit and connects'the upper winding of relay 236 directly to the loop circuit; atlarmature 241 closes a locking circuit for its lower winding to groundinthe'- release-trunk; and at contacts controlled by armature 242disconnects the lower winding of relay 236 from the trunk and closes ashort circuitaround condenser 237 including armature 245 of relay 234.The trunk circuit has now been changed from .the loop type to thesimplex type. The upperi winding of relay 236 is now connected with bothconductors of the trunk by way of armature 240 of Y relay 232, contactscontrolled by armature 243 of relay 233, contacts controlled by armature246 of .relay 234,v and the short circuit around condenser 237previously closed by relay 232. Relay '236 remains operated 'over acircuit which will be described hereinafter.` Y y 'f Relay 233 isconnected to meter leadk220 and operates with each metering impulsetransmitted over the lead from repeater OR2. Relay Y 233 on operating,at contacts controlled by armature 243,disconnects the upper winding ofrelay 236 from 'the trunk conductors and connects it to aholdi'ngground. The simplex trunk is therefore cut dry with eachmetering impulse, that is, battery through the upper winding of relay236 is disconnected. l f

VCurrent flow was reversed inthe control loop extendingvfrom. repeaterOR by the operation of relay 234'in repeater IR. The reversal of currentliowv in the loopV which includes the upper winding of relay 201, causesthe two windings of this relay to assist cach other and the relayoperates. Relayr 201 on operating short circuits condenser 209 atarmatures 210r and 214. A branch of the short circuiting lead extendsthrough the lower winding of relay 203 to ground. Ground through relay203 is thus connected to both sides of the trunk and serves to maintainrelay 203 and also relay 236 of repeater IR energized over a simplexcircuit including both trunk conductors. vRelay 201 at varmature 211also opens the initial energizing winding of relay203, and closesalocking circuit for its own lower winding by short circuitingresistance 206; at contacts controlled by armatures 212 and 213 reversesthe current flow over trunk conductors 167 and 168l in the usual manner;and at` armature 215 closes a point in the metering circuit includingconductcr170. Y

As previousy described, metering impulses transmitted from repeater @R2cause the periodic operation of relay 233 ot repeater IR which onoperating` cuts the simplex trunk dry byV disconnecting Ybattery whichis fed tothe trunk through the upper winding of relay 236. Each timebattery is disconnected Afrom the trunk, relay 203 ot` than theV unitcharging interval-,the second" revolution of the wipers of rotaryfswitchRS associated with repeater OR?A will cause thiz meter to registeragain. Thus at vregular pre-determined intervals during the course ofthe connection, the meter will be operated to registerthe charge on thebasis of duration of the'call.

tjthe termination ofV the conversation both subscribers will restoretheir receivers. li the called subscriberhangs up lirst, no-th" inghappens, as the connector is ordinarily arranged for release by the lastparty. The connector, however, maintains the ground on the upper trunkconductor so that the'callsubscribers meter will continue to reg isteruntil the receiver is restored. lVhen the calling subscriber restoresthe receiver at substation A. the Gallinoloo will be opened at theswitch hook springs inthe usual manner.` Relay 2020i repeater OR whichwasenergized over the loop will retract its armatures, opening thesimplex circuit to'repeater IR inthe distant oiiice, and opening thecircuit of relay 204. .Relay 204 restores, removes ground from therelease trunk conductor 169, opens, the holding circuit oi2 relay 201,and opens a point in the simplex circuit'to the switch ahead.V Relay 205deenergizes assoon as ground is removed from the release trunk andswitches the trunk conductors 207 and 208 back to incoming connector C1.

tors in the normal manner. Relay 203 ref stores when the second pointVin the simplex circuit is opened by relay 204.- The repeater is now innormal condition.k x 1f i `The removal of ground fromthe release Relay201 restores and ref connects line relay 202 to the 'trunk conclue-'trunk asabovedescribed causes relays 111 ,i

and 101 of connector C, and relayr3 oflin'e switch LS to deenergize.Relay 111 on re- 4 storing disconnects the line wipers from thetalkingconductors, connects test wiper 117V,

in the normal testing circuit andclosesa point in the circuit oftherotary magnet. Relay 101 on restoring switchesthe trunk conductors backto line relay 103,A opensa point in the' metering circuit,v andcloses `acircuit for the release magnet including armature 129 of relay 103,armature 131 Aof relay 104, andV operated oi-normal spring contacts120;V Release relay 114 energizes and permits the switch shaft andwipersto restore to normal in the usual'mannen Theshaft von reachingits normalposition opens the circuit `ot. therelease magnet-, at the o'tl'fnormal`springs, and closes a part of the normal energizing circuit otrelaysv104 and 105.

` Relay 3 of theline :switch LS restores and reconnectstlie 4lineconductors to line relay l 233-restores1f `Relay 236 opens theloop'circuit to the succeeding` switch and also opens thecircuitbfrelay231. Relay 2,31 deener-V` V4 and' `ground respectively. i The wipersre-l l mainfon .thecontacts of the trunk Just used..V

W hen. the control" loop isV openedin regia-es and removes ground tromVthe release trunk conductor'- 239 and also disconnects rebusy conditionbeing removed, repeater ORl rcan now -be seized for another call. Groundbeing removedA from the "release trunk, re-

lays 232 and 235 deenergize'. Relay 232 on Y,

restoring changes the simplex holding cir cuit back to a loop'circuitand opens itsf o wnholding winding. Relay 235 on deenergizing Y Vopensthe circuit of relay 234,-which restores and connects relay 236 to thetrunk conduc- A tors in the normal manner.V

The removal Voi. ground from release trunk Y conductor permits therestorationvof relay 305 of selector'S; Relay 305 closes the usual Ycircuit for the release magnet which causes r- The holding loop forrelay'404 of repeater OR; being openedV at repeater IR, this relaydeenergizes.V Relay404 opensl apart of the loopfcircuit to the 'switch'ahead and opens the circuit of relay 406. Relay 406 deenergizes andopens thecircuit` of relays 401, which operatedV momentarily when relay404 deenergized; opens the holding circuit `of relay 405 and removes theVadditional holding The release lease trunk 'conductor 282 of repeater0R,L 490 V from ground and connects it to relay261. The

1110V f Y ground from the release trunk to the preceding switch.

Relay 402 deenergizes inmediately after the release of relay 401, itsinitial energizing circuit being open at contacts of relay 404 which hasdeenergized. Relay 407 deenergizes as soon as ground is removed from therelease trunk and switches the trunk conductors back to incomingrepeater lRl. Relay ,405 deenergizes and opens a point in its ownholding circuit, opens a part of the circuit of relay 403, disconnectsmetering conductor 332 from pulsing mechanism M, connects a ground totheright hand bank contacts of rotaryswitch RS, and disconnects theinterrupter lead from the rotary magnet. lf the wipers ot rotary switchRS are in their home position no action takes place; however, if thewipers are in any other position a circuit for the rotary magnet will beclosed includingarmature 419 'and' normally closed contact of relay 405,right hand bank contact of switch RS, wiper 431, and rotary interruptersprings 435. `The rotary magnet energizes, opens its own circuit at theinterrupter springs, and in deenergizing steps the wipers ahead. Thisoperation 1s repeated as longv as wiper 431 encounters a groundedcontact. wWhen the home contact is reached, no ground being foundthereon, the stepping operation ceases. All relays of repeater @R2having restored, the switch isl now in normal condition.

The loop circuit for relayV 503 beingopened at repeater ORz, the relaydeenergizes and opens the circuit of relay 504, and closes a circuit forrelay 505'. Relay 504 deenergizes, opens a point in the circuit of relay506, opens the circuit of relay 505, disconnects signalling lead 531from ground and connects it to cutoff relay 501, and removes ground fromrelay 507 and control Ylea-d 510 to the selector. Relay 505 deenergizes,the' momentary energization when relay 503 restores has no utility.Relay 506 deenergizes and opens a point in the circuit of relay 502.Relay 502 deenergizes and again connects the lower winding of y relay503 tothe trunk conductors. Relay 507 restores and disconnects trunkconductors 508 and 509 from the repeater.

In selector S2, relay 533 deenergizes when ground is removed fromcontrol lead 510. Relay 533 disconnects relay 534 from control wiper 554and closes a part of the release circuit. Relay 534 restores,disconnects Vwipers 552 and 553 from trunl7V conductors 508 and 509 andcompletes the circuit of the release magnet kincluding operatedcontacts557 ofthe oli-normal springs. The release magnet energizes, the shaftand wipers return to the normal position in the usual way.,-

and the circuit of the release magnet is again opened at the off-normalsprings.

The local switch train following selector S2 releases m the'well knownmanner.

It will now be assumed that the subscriber at substation A in X oliicedesires a connection with a subscriber in a nearby town to which asuburban service is maintained. The calling subscriber dials the digitsrequired for reaching selector S2 asY described in the precedingconnection and is connected with selector S2. Assuming that thesubscriber now dials the digit 0, selector S2 operates as describedbeterel and selects an idle trunk on the tenth level, for example thetrunk com.- prising conductors 564 to 566, inclusive, terminating oncontacts 555 to 557, inclusi-vc, leading to operators position OA.

It will be recalled that selector S2 extended a ground through relay 534over control wiper 554. VThis ground extends byk way of contact 550,conductor 557, through the short circuit around the upper windingotrelay 572 including armaturesr57 3 and 575 of relays 571 and 572,respectively, t irough the lower winding of relay 572 to battery. Relay572 eneroizes and opens the short circuit around its upper winding.Relay 572 remains enerfrized over both windings in series and' atarmature 576 closes a circuit for the supervisory lamp includingarmature 57 470i relay 571. he supervisory lamp now burns to inorm'theoperator that a call has been eX- tended.

To answer the call, the operator inserts the answering plug of aregularcord in the answering jack and establishes a talking connectionwith the calling party in the usual way. rllhe insertion of the pluginto the jack also closes an obvious circuit for relay 571 whichoperates, opens another point inthe short circuit around the upperwinding ot relay 572 and opens the circuit of the super-4 visory lamp.The supervisory lamp is now extinguished at all positions in which thetrunk is multipled, indicating that the call has been answered.

The operator determines the number of the wanted subscriber and extendsthe call by means of the other plug of the answering cord. Y

When the calledV subscri1 er answers,` the operator is so informed bythe usual supervisory sien als in the cord. The operator thenmomentarily depresses the meter key, which connects ground to trunkconductor 564 at contact 577. Relay 506 ot repeater IR2 operates fromthis ground in the same manner as when the connector placed a ground onthe upper trunk conductor. Relay 502 operates and connects both windingsof relay 503 in series in the control loop whereon relay 402 of repeaterdeenergizes as previously described. Tlie operationv of relay 405 andmetering device M takes place in the same .manner as on a call to asubscriber iny Z otlice.

The-.operator then releasesrthe meter key which removes the ground fromconductor 564 Y whereon relays 506 and 502 of repeater IR2 restore. Thelower winding only of relay 503 is now connected in the control loop andrelay 402 again attracts its armatures. Relay 405, however, remainslocked up through its` upper' armature. Relay 402 on energizing closes acircuit for relay 403 including armature 415 of relay 405 and the upperar` mature 409 of relay 402. Relay 403 operates and at itsrupperarmature closes a locking circuit for itself independent of thecontactsof relays 402 and 405. RelayA 403 at armature 411 connects anothercontact of the left hand bank of'rotary switch RS to the meter lead 332.`With each revolution of theA wipers, two metering impulseswill betransmitted as wiper 430 passes over` contacts 432 and 433 ofthe bank.rIhe metering impulses are repeated back tov the calling g subscribersmeter in the same manner as previously described for calls to Z oicesubscribers.

At the termination of the call,.the'oper ator receives the usual cordsupervision when either party .hangs up.k The operator then removes .theplug from the answering .jack and the switches restore to normal aspreviously described. Y i i 'I'he operations involved in setting Vup acall from the subscriber atsubstation A (Fig. 1) in X oiiice to thesubscriber at substation A3 l7) in Y ollice will'nowbe. considered.V Thesubscriber at substation A lifts the receiver and dials the digits Oand1 calling loop through repeaters OR and IR t0l selector Sf exactly asdescribed for a call to Z oce. rIihe third digit operates selector Swhich selects an idle trunk as previously described. It will be assumedthat the third digit dialled was 9 and that the wipers of selector Sstop'on contacts 325 to 328 associated with the trunk comprisingconductors 325 to 328, inclusive, terminating in connector C'g (Figi').l

Connector C2 is an ordinary Strowgertype connector, the operation ofwhich is well known in the art. It is therefore thought unnecessary todescribe its operation in detail. When selector S switches through, thecontrol loop from repeater IR is extended t0 line relay 702 of connectorC3. Line relay 702 and release relay 703 operate in the usual manner.The subscriber then dials the last two digits of thev called number,theinterruptions of the loop being. repeated by repeaters OR and IR aspreviously described.

Line relay 702 of connector G3 operates in response to the repeatedimpulses and completes the usual vertical and rotary stepping circuits.The wipers 735, 736 and 737 of the connector Awill be advanced to thecontacts of the called line .which will be assumed to be contacts 738,739i`and 740 associated will encountera ground `on contactV 740 and testrelay 7 0610il the connector will. operate."

which permits the back contacts to open but L prevents the frontcontacts from closing. This. cuts od the normal battery and groundconnections from the line but d oes not close through a. circuit to thewipers. i

When the calledA subscriber lifts the receiv-v er at substation A3, adirect current circuit is closed for the upper winding of ring-cutofi'relay 705 of the connector.V Relay 705 Ifthe called'linev is idle,

operates and inl the usual manner cuts oli' the ringing current andconnects the talking conductors through to the baclt-bridgeirelay 701.

Relay 701 feeds batteryand ground to the called line. and operatesoverVthe calledv subf scribers loop. Relay 701 on operatingreverses thetrunk conductors withv relation'to line` relay 702 Vwhichreverses thedirection of the currentflowin the control loop. `Relay 2350 repeater IRoperates when-the current flow is reversed in the control loop,` and'.

changes the control loop between repeaters @Rand IR to a simplexholding-circuit as described under calls to Z oliice.` As inthepreviously described connectioinrelay 236 through its upper winding andrelay 203 through its lower winding are energized in series over thesimplex circuit.

When relay 705 of the connector operates it also connects battery tometering conductor 344 through resista/.nce 709.*Y VRelay 233 of refpeater-IR operates vfrom this battery,- closes Va holding circuit forrelay 236 and cuts oflthe battery from the simplex circuit. Relay 203 ofrepeater OR deenergizes and closes the metering circuit as previouslydescribed which causes the meter associated with line switch LS tooperate. i

During the conversation the voice currents will be transmitted over thedry simplex circuit to repeating coil R by which Vthe simplexcircuit isinductively connected to the calling subscribers loop. Atthe end ofthe.conversation, both subscribers Willrestore their receivers andtheswitches will release Y in the Vmanner previously described. It is thecalling subscribers meter]V will register only'once on calls from X to Yoilice. g i The connections dealt Vwith,up to this time have involvedtrunl'ring between two or more offices. The operations involvedV in aVcall from substation A to substation A1, v bo-thin y X office willnowbe considered.

1 When the subscribe-r at substation lifts the receiver, line switchoperates as previously described and selectsan idletrunk which will beassumed to be the trunk terminating in connector C. Connector C respondeto the rst digit in the same manner as described under trunk calls andsteps the wipers to the called level. It will be assumed.V

that the digit 9 is dialled and that the wipers are raised to the ninthlevel. Y The operations so far have been exactly the same as for trunkcalls except that the shaft springs are not operated when the shaft andwipers reach the ninth level. The connector now responds to the seconddigit which will be assumed to be a 5 and the wipers are rotated intoengagement with contacts associated with line 95. This line for examplemay be the one comprising conductors 171, 172 and 173 terminating oncontacts 163, 164, and 165 and leading to line switch LS', associatedwith substation Al. Contact 166 of the banks is multipled with Contact165 on individual lines.

1f substation A is busy, test wiper 117 will encounter a ground onvcontact 165. Referring to the first connection described, it will beunderstood that relays 109 and 110 of connector@ are-operated during therotary iinpulsing. Relay 108 which is connected tothe test wiper by wayof contacts controlled by armature 149of relay 110 operates from theground encountered by the test wiper. As contacts`165 and 166 arestrapped together, wiper Y118 will also encounter a ground. Shortlyafter the last rotary impulse relay 109 deenergizes and at armature 1115closes a circuit for the lower winding of relay 110 to ground on wiper118. As previously eX- plained, the two windings of relay 110 opposeeach other and vthe relay deenergizes. Relay 109 on deenergizing alsocloses a point inthe circuit of relay 107 but this relay does notenergize since its circuit is also opened at armature 152 of relay 110which is now deenergized. Relay 108 on operating closed a point in itsown locking circuit, closed a point in the circuit of the upper windingof relay 110, opened the rotary impulsing circuit, and closed a point inthe busy tone circuit. Relay 110 on deenergizing opened the circuits toboth its upper and lower windings, disconnected the test wiper fromrelay 108 and closed a point in the locking circuit of that relay,removed the shunt around the armature lil-3 of relay 108, opened a pointin the circuit of relay 107 and closed'a pointl in the busy tonecircuit. Busy tone is now applied to the lower talking conductor toinform the calling subscriber that the called line is not available atthis time. The calling subscriber then restores the receiver andconnector C and line switch LS return to normal as previously described.y

In case the called line is idle, the ltest wiper will find batterypotential on the testcontact and relay 108 will not energize. When relay109 falls back shortly after the last rotary impulse, the circuit of theupper winding of relay 110 will be opened. Relay l110 on deenergizingswitches the test wiper from relay 108 to the lower winding of relay111. A circuit is thus closed from ground 4on the release trunk,contacts controlled by armature 155 of relay 1 11, armature 141 of relay108, lower winding of relay 111, armature 149 of relay 110, test wiper117, test con'- tact 165, conductor 173, winding of relay 3 of lineswitchy LS1, interruptor springs 17 winding of magnet 5 to battery.Relay 111 operates over the abovetraced circuit and at armatures 154 and158 connects the line wipers to the ringing equipment; at contactscontrolled by armature 155 opens a part of the circuit of its own lowerwinding and connects testy wiper 117 to they grounded release trunk; atarmature 156 closes a locking circuit for its own upper winding; Vand atarmature 157 opens the circuit of the rotary magnet. v

Relay 3 of line switch LS'l energizes in series with relay 111 andmo-ves its arma-` tures far enough to open the back contacts but notenough to close the front contacts.

The complete stroke of the armatures is pre-V ventedby a mechanicallocking device controlled by line relay 4E and is well known in the art.r1`he partial'operation of relay 3 disconnects the normal battery andground connections from the called line. y

Ringing current is now automatically sent over the line at intervalscontrolled `by the ring interrupterto operate the bells at substationAl. It will be noted that the ringing circuit includes theV lowerwinding of relay 106, and that during the silent period aV ground isconnected to the lower trunk coii- Y ductor. When the called subscribedat substation A1 answers by lifting the receiver, a direct current pathis closed over which relay 106 energizes, Relay 106 on energizing, atarmatures 135 and 138 opens the ringing circuit and switchesthe calledline loop through to back bridge relay 102; at armature 136 connectsbattery to metering conductor 21; and at armature 137 `closes a lockingcircuit for itsown upper winding. Relay 102 feeds talking battery to thecalled subscriber and operates over the called subscribers loop. Relay102 on operating Vreverses the trunk conductors with respect to linerelay 103 by means of the usual reversing circuit. The reversal ofbattery has no utility in this connection. The meter associated with thecalling line switch LS energizes from the battery on the meteringconductor.

At the termination of the conversation, both subscribers replace theirreceivers and the switches release-as previously described.

The meter associated with line switch LS Y remains energized throughoutthe connection and consequently registers only once for J. i Y the call.

A call from the operator Z otlice toa subs'criber at substation A willnow be described. The operator observing that the trunk circuit OC isidle, inserts the calling plug of a armature 511 of relay 501, trunkconductorV 428, armatureV 425 of relay 407 in repeater OR2, upperrightliand winding of repeating coil R4 `associated with repeater IR1,upper winding of relay 451, normally closed lcontacts controlled byarmature 456 of relay 452, lower right handwinding oi repeating coil R4,arma-ture 427 of relay A407, trunk conductor 429,'armature 512oi'relay501,

lower left hand winding ot repeating coil R6 to ground. Relays 591 and451 operate over the above circuit. Relay 591 on operating opens theshort circuit around condenser 584 and this opens the loop through theoperators cord circuit extinguishing the supervisory lamp (not shown).Relay 451 onoperating closes an obvious circuit for relay 453 and alsoVcloses a part of the loop circuit to the line relay of incomingselector S1. V Relay 453 on operating at armature 457 opens the circuitof relay 407 and grounds the release trunk of repeater OR2 to mark thatrepeater busy; at armature 458 completes the loop circuit to selector S1including the Vupper winding of polarized relay 452 and impedance coil454; and at armature 459 closes a circuit for Jthe lower winding ofrelay 452. Relay 452 does vnot operate at this` time as its two windingsoppose each other.

l .Selector S1 is exactlythe same as selector S previously describedand, therefore, its

operation will not be described in detail. The lineV relay energizesover the loop ex-V tended by repeater IRl. The selector is now ready toreceive the iirst digit.

In order to dial, the operator presses the dial key which is a lockingkey. At contacts 586 and 587 the battery feed to the control loop istransferred from the lower winding of relay 591 to resistance 583through the impulsing contacts of the calling device or dial. A lockingcircuit for the upper winding of relay 591 is closed at contacts 585 tokeep this relay energized during the dialing so that normal vsupervisionwill be given in the cord circuit. The operator then dials the lirstdigit. Assuming the first digitto be an 0, the control loop ismomentarily opened ten times. Relay 451 oi" repeater IRl responds to theinterruptions and' at in turnrepeats the'int armature 458 interrupts theloopto selector S1 a like number of times. TheV line relay of selectorS1 responds to the loopl interruptions in the usual way and the wipersof the y i selector are advanced to the tenth level. The4V switch thencutsV in and-rotates the wipers@ Y into engagement with the contacts ofan idle trunk, for. example contacts471 to474, in-

elusive, associated with the trunk compris-f` ing conductors 280` to`283, inclusive, termi# nating 1n outgoing repeater 0R11, l

. The control loop is thus extend ld from refM way. of wipers 461 and462, contacts 471"a1 id"472;l

peater IRM through selector S1- by trunk conductors 280 gandf28l, rightlhand windings of repeautingv coil R2 of repeater y ORl, normallyclosed` contacts controlled by` armatures 271 and Y272 of relay 263,through the upper and lower windings oirelay264y l tov battery andground'respectively. The r`e lease trunk -is extended from the selectorby way of; wiper 464, contact 47 4, conductor 282,

armature 239 of relay 231 of repeater IR, to y -relay 261 of repeaterORl; Re'lay`261oper--V ates and switches trunk, conductors 207 Vand 208from repeater IR to repeaterORll The `metering conductor is alsoextended'from se-A y lector S1 by way owiper 463, contact 473,` V Y andconductor 283 to repeater @R1 but has no utility in this connection.`Relay 264 operates over the loopV extended from repeater IRM' closes anobvious circuit for relay 2,651'and completes a loop circuit to theline` relay `of incoming connector C1, including trunk co-n ductors 207and 208, armatures 268 and ,269i of relay261, armature 274 of relay264,1ett hand windings of repeating coil R2, resistance 267 andupperwinding of polarized relay 262. ground on the release. trunktoholdup `selector Sl and to maintain relay 261 energized, and closes acircuit for the lower wind-y Relayl 265 operates and places.'` 5

ing ofrelay 262. Relay 262 does not operate. y

at'this time as'theV two windings opposeeach V n 1 1,10

' i 1 A r ConnectorCl is exactly the saine as lconnector C and it istherefore unnecessarylto ex.-`

plainits operation in detail. Tlieline relay,

corresponding to relay 103 ofconnfector C, energizes over the loopextended from repeaterjOR]L and` closes the circuit ot--relay 104 whichcorresponds to release relay 104 of connector@ Relay 104 grounds therelease trunk of connector C to mark `that switchbusyvand opens` thecircuit of cut-oli" relay` 205. `The second and third digits are nowvdialled by the operator.` The loopinterrupti-ons are repeated by .relay451 of re-` peater IRl to relay 2640i repeater ORlywhich. err'u"` tions.V,to the line l' relay of the manner and eladvancedto relay of connectorC connector responds'i; wipers 116^ an the contacts of the assumed tobe' cont high wiufbe. i

13o y f

